Circuit breaker trip mechanism



Nov. 4, 1952 D. l. BOHN 2,616,999

CIRCUIT BREAKER TRIP MECHANISM Original Filed Dec. 8, 1943 5 Sheets-Sheet l All as mo 7/ ha) i 75 -& 34

l 263 //a 8,3 64 we as 93 aa zzz fi Ill IN VEN TOR.

DONALD [Bo/4w fig. 13. BY

Law/v Nov. 4, 1952 D. 1. BOHN 2,616,999

CIRCUIT BREAKER TRIP MECHANISM Original Filed Dec. 8, 1943 5 Sheets-Sheet 2 IN VEN TOR.

.Dfl/VALD BOH/V Nov. 4, 1952 D. 1. BOHN 2,616,999

CIRCUIT BREAKER TRIP MECHANISM Original Filed Dec. 8, 1943 5 Sheets-Sheet 3 Ego 5 IN VEN TOR.

.DO/VAL D K B OI /N BY wwww Nov. 4, 1952 D. l. BOHN 2,616,999

CIRCUIT BREAKER TRIP MECHANISM Original Filed Dec. 8, 1943 5 Sheets-Sheet 4 fig- Z INVEN TOR.

DONALD [BDH/V BY @m v Nov. 4, 1952 D. L- BOHN CIRCUIT BREAKER TRIP MECHANISM Original Filed Dec. 8, 1943 5 Sheets-Sheet 5 Fig. 5.

IN VEN TOR.

DONALD BOH/V Patented Nov. 4, 1952 CIRCUIT BREAKER TRIP MECHANISM Donald I. Bohn, Pittsburgh, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Original application December 8, 1943, Serial No.

513,418, now Patent No. 2,543,398, dated February 27, 1951.

Divided and this application September 20, 1949, Serial No. 116,773

4 Claims.

My invention relates to a new and improved circuit breaker and is a division of my co-pending application Serial No. 513,418 filed December 8, 1943, now Patent No. 2,543,398 dated February 27, 1951.

My invention incorporates an overcurrent trip means with the holding magnet and armature set forth in my above-mentioned copending application.

An objectof my invention is to provide circuit breaker contact separation by means responsive to current drop, reverse current flow, excess current flow, and predetermined overload currents of relatively low rate of rise.

A further object of my invention is to provide a means comprising a manually operable member to permit contact separation.

The foregoing and many other objects of my invention will become apparent in the following description and drawings in which:

Figure 1 is a schematic view showing the closed circuit position of the clutch and operating members.

Figure 2 is a schematic view showing the initial tripping operation when the clutch is released.

Figure 3 is a schematic view showing the clutch and operating parts moved to the full open position.

Figure 4 is a fragmentary view of a portion of the manual trip mechanism.

Figure 5 is a side view of the magnet of the operating mechanism.

Figure 6 is a top view of the magnet and armature assembly.

Figure '7 is a view partly in cross-section showing a novel selective tripping device for use with my invention.

Figure 8 is a view partly in cross-section taken on line 8-8 of Figure 7 looking in the direction of the arrows.

Figure 9 is a view partly in cross-section taken on line 99 of Figure 7 looking in the direction of the arrows.

Figures 1 to 3 show schematically fixed movable and arcing contacts 26 and 35 engaged, respectively, by the movable contacts 32 and 36 carried on the pivoted arm 34. Arm 34 is pivotally connected at II to the spring operated arm I10, one end of which is secured to a spring I88 tending to move arm I10 to the right to efiect disengagement of the contacts.

The other end of arm H is secured through extension I to the lower clutch member I8 having a notch or detent 82 of substantially rectangular cross-section in which there is seated 2 a roller 83. The roller 83 also seats in a notch 86 of a pivoted arm 84.

It will be obvious that so long as the roller 83 is seated in the two complementary notches 82 and 86, it acts as a stop to prevent the spring I from efiecting disengagement of the contacts.

The spring I 80 acting through arms I10, 15 and I8 urges the left-hand side of notch 82 against the roller 83, tending to move the roller to the right until it engages the right-hand wall of the notch 86. This is the condition obtained in Figure 1.

The right-hand edge of notch 86 engages the roller 83 at a point which is slightly above the horizontal diameter of the roller 83. Thus, the force of the spring I80 may be regarded as made up of two components, the larger component exerting a force against the roller 83 pressing it against the right wall of notch 86 of pivoted arm 84. The other component tends to rotate the roller 83. This component force may be made very small by bringing the plane of the line of contact of notch 82 to spring I80 close to the center of the roller 83.

In order to overcome this rotative force and to hold the roller 83 in the notch where it acts as a stop, the holding magnet I80 through its armature IIlI and link I 02 engages the pivoted arm 84. The hold-down springs I89 which engage the magnet then exert a downward pull on the magnet and hence on the pivoted arm 84 to ensure enagement of clutch members 84 and 18. This downward force need only be just sufficient to overcome the small rotative component of the spring I88.

The magnet I00 and the armature IIlI may be constructed exactly as shown in Patent No. 2,412,247 issued December 10, 1946, assigned to the assignee hereof.

This structure, as above pointed out, requires the exact alignment of the notches with a specific line along the roller. Therefore, link I02 must be so arranged as not to interfere with this alignment. This is accomplished by fioatingly supporting the magnet in the manner hereinafter described and :by biasing the magnet downwardly by springs which exert a force on the magnet away from the armature with a pull equal to or slightly less than the magnet pull on the armature, i. e., 340 pounds. The magnet structure thus automatically positions itself to maintain a force, through link I! and arm 84, of 340 pounds to hold the roller against rotation.

The circuit breaker of this invention has gen- 3 erally the construction and operation shown in Patent No. 2,150,566 to William M. Scott, Jr. and assigned to the assignee of the present invention in which the holding magnet of the type shown in Patent No. 2,412,247 issued December 10, 194.6 is incorporated.

The movable arcing contact 32 and the movable main contact 33 are mounted on the contact carrying arm 34 which is pivoted on pin 10. Spring 1811 exerts a biasing force on link 110 tending to pull it to the right and, therefore, exerts a clockwise bias on the contact carrying arm 33, thus tending to open the contact members. This opening bias on the part of spring 1 80 is resisted by means of link '13 also pivotally connected at one end to the pin '11 and at the opposite end pivotally connected to the pin 1'1 of the lower clutch member '18.

The lower clutch member '18 is mounted in a manner hereinafter described so that it may slide longitudinally from the position shown in Figure 1 within the housing 80 to the position shown in Figure 3 still within the housing.

When the lower clutch member 18 is released from the engagement with other elements of the clutch, hereinafter described, then no further resistance will be offered to the bias of the spring 180 and the spring may then move the clutch element 18 from the position of Figure 1 to the position of Figure 3, thus moving the movable contacts in the manner shown.

As long as the upper pivotal arm 84 pivotally mounted within the housing 80 on the pin 85 is held down in the position shown in Figure 1, then the interengagement of the arms 88 and '18, by reason of the roller 83 restin in the complementary detents, prevents the longitudinal movement of the roller 83, and clutch member '18, and hence prevents the spring 180 from being effective to separate the contacts.

The instant the pull of magnet 100 on the armature 101 is neutralized due to circuit conditions, the downward pull of 340 pounds on the arm 81 is released, and then the bias of spring 180 will be effective to produce the results shown in Figures 2 and 3; that is, first the roller 83 will be rolled out of the complementary detents 82 and 80 onto the surfaces of the members 18 and 8 1, thus causing the clutch arm 84 to rise; and then as the roller is completely freed from the detents by this operation, the spring 180 is permitted to be effective to move the elements further from the position shown in Figure 2 through to the position shown in Figure 3 where the contacts are open.

I have found that by this arrangement a holding force of less than of the opening bias need be used to maintain the circuit breaker closed.

Thus, while the downward pull applied to the arm 88 is of the order of 340 pounds, it will safely retain the contacts in the closed position even though the opening bias of the spring 180 is of the order of 5,000 pounds.

Assuming that little or no force is applied to hold the arm 84 down while the full opening bias of spring 180 is effective on the lower member 18 and assuming that the arm 84 is freely rotatable upwardly around the pin 85, it will be obvious that the successive results shown in Figures 1, 2, and 3 will occur; that is, the roller will roll up the left hand side of detent 82 and down the righthand side of detent 86 in response to the longitudinal pull on the member '18 in the manner previously explained.

But when a downward pull is exerted 91!- he upper clutch arm 84, the pull on member '18 is transmitted from the left-hand side of the detent to the roller 83 and from the roller 83 to the right-hand side of detent 86; and since the righthand side of the detent 88 is substantially tangential to an imaginary circle drawn about the shaft as a center and since the pull is thus normal to the initial direction of movement of the arm 81, a relatively small force is all that is necessary to restrain the arm 80 from rising despite the fact that a relatively great force is exerted on the member 18.

However, and this has been demonstrated by the fact that in an actual commercial embodiment of my invention the holding force which holds down the arm 84 exerts less than onetwelfth the pull exerted by spring (340 pounds to 5000 pounds), when the holding force is released from the arm 84 the successive results shown in Figures 2 and 3 occur.

The circuit breaker is also arranged so that it may readily be manually tripped. This operation will be clear from an examination of Figures 4, 5, and 6.

The front end of shaft 304 is provided with a handle 305 which is rotatably mounted on the extension of the shaft 304 outside of the housing.

A lug 386 is keyed to the shaft 304 in any suitable manner, and a screw 30'! is threaded through the handle and engages against one surface of the lug 308.

Rotation of handle 305 in a direction to bring screw 30'! against lug 306 will rotate shaft 30 rotation of the handle in an opposite direction will have no effect.

The shaft 304 is provided with an eccentric crank element 310 which passes through an opening 311 in the lower end of the link 312, which link is secured on the crank element 310 by means of the washer 313 and the cotter pin 31 1.

The upper end of link 312 has secured thereto by means of the rivets 315 and 316 a threaded extension 311 which may be screwed into the threaded socket of the trip link head 318 and tightened therein by the nut 319. Trip link head 318 is pivotally secured at 320 to the bifurcated link 321.

Link 321 is secured to the shaft 322 which is rotatable in the bearing boss 32'! of the housing 80, Figures 5 and 6. Shaft 322 is secured to yoke 335 which engages with the yoke 338 secured to shaft 325 which is rotatable in the bearings 323, 323.

An eccentric portion 324 of the shaft 325 underlies the lever or arm 249 of armature 101.

Rotation of shaft 308 by means of the handle 305 thus results in lowering of the link 312 which, in turn, rotates the bifurcated link 321, the shaft 322, and the yoke 335 which in turn rotates yoke 336 thereby turning shaft 325, thus lifting the eccentric portion 324 of shaft 325 and lifting the arm 283 of armature 181. The armature is thus pushed upwardly from the magnet.

As pointed out in the co-pending application previously referred to, the moment even a slight separation of the armature from the magnet occurs, the holding force on the armature drops, and the armature 101 is free to be pulled away from the magnet 100. It is obvious, of course, that the armature 101 is secured by the arm 2:19 on the shaft 330, and coil spring 331 biases the armature 101 toward the magnet 10111.

An overcurrent trip may be provided, as shown in Figure 5 which comprises the armature 350 pivoted on the pin 35'1.

The free end of the armature 350 is ordinarily held down by means of the tension spring 35I connected between the pin 352 on the armature 350 and the adjustable lug 353 on the adjusting screw 354.

In the event of an overcurrent condition in a forward direction (rather than a reverse current condition), the armature 350 is attracted by the magnet I and rises toward the same against the bias of the tension spring 35 I. The armature 350 is thus brought into contact with the pin 356 which rides in a suitable slot in the magnet itself.

The upper end of pin 356 bears against the reverse current armature IOI. Thus, when the forward overcurrent armature 350 is attracted to the magnet I00, the pin 355 is pushed up to push armature IOI away from the magnet I00, thus resulting in a tripping of the circuit breaker.

Circuit breaker actuation depends upon the direction and intensity of the current flow. From Figure 7 it will be seen that two paths 5656 and bucking bar 50 are provided for the flow of current as described in my co-pending application Serial No. 513,418 filed December 8, 1943, now Patent No. 2,543,398 dated February 27, 1951.

In order to control the amount of current flowing through these paths, a quantity of inductive iron 58 is placed around one of them. When there is a sudden increase of current flow in either direction, part of it is retarded from flowing through 56--56 due to the inductive iron 58. The remainder, following the path of least resistance, will pass through the bucking ba 50. The amount of current retarded depends upon the steepness of the wave front of the current increase.

The magnet I00 is provided with the independently energized shunt coil I03 which creates the initial bias thereon to attract and hold the armature IOI. The flux generated by the shunt coil I03 energizes the magnet by means of pole pieces I03 in a manner previously described in Patent No. 2,412,247 above-mentioned.

If the current flow is opposite to the normal direction of the current flow in the breaker, it will oppose the magnetic field in the magnet I00 set up by the independently energized shunt coil I03 and so reduce the attractive power of the magnet that the armature IOI will pull away, and the breaker will function as described in the specification.

On the other hand, if the flow of current is in the normal, or forward direction, it will be in the same direction as that of the shunt coil I03, and will add to the flux already established in the magnet I00. When it reaches a predetermined intensity, it will set up suflicient attractive force to draw the armature 350 against the bias of spring 35 I up against the lower pole face of magnet I00. This action, as can be seen in Figure 5, causes the plunger 356 to pry the armature IOI away from the upper pole face of magnet I00, thereby breaking the attraction of the magnet for the armature I M and thus permitting the breaker to function as designed.

The conditions described are for predetermined rates of rise within calibrated limits. Excessive surges of current, due to short circuit, will cause a similar action to take place.

In a preferred form of overcurrent and reverse current control shown in Figures 7, 8, and 9, part of the inductive iron 58 is removed from conductor 56-56 and replaced with a field structure 400 and an armature 40I. In the case of a forward overload in the main circuit of a predetermined intensity (in the neighborhood of 8000 to 12,000 amperes), the armature 40I will be attracted by the magnet 400, actuating a switch 402 that deenergizes the potential coil I03 which, in turn, causes the collapse of the field in the magnet I00 and allows the breaker to function as described above.

In the case of an overload having a steep rate of rise, the magnet 400, being on the same leg of the circuit as the rate of rise iron 58 (or inductive iron 58), most of the current will be by-passed through the bucking bar 50. Thus, the magnet would not give overload protection until the value of current in the main current carrying conductor was dangerously high. Therefore, an additional tripping device is required for short circuit current protection.

When sudden and excessively high surges of current caused by a short circuit or when the values of current go from 16,000 to 24,000 amperes or higher, the field structure 500 attracts the armature 50I which lifts the lever 502. This lever, being pivoted at 503 and contacting the manual trip lever 3I2 through stud 504, depresses the manual trip lever 3I2, which in turn pries the armature I M off the upper pole face of magnet I00 and actuates the breaker. The action of the manual tripping device 3I2 has been previously described.

Since the magnet 500 is on the main current carrying conductor, it is only affected by the value of the current passing through it. When it is calibrated at 100% of overload it will be unaffected by peaks of current of short duration as long as they are not in excess of 100% of overload. However, magnet 500 and armature 50I will function instantaneously on high values of current.

From this it is evident that the magnet 400 is required to give normal overload protection, while the magnet 500 is operative on short circuit currents or other excessively high current values which require rapid opening of the breaker.

The location and adjustment of these devices determines their selective operation. In the case of the magnet 400, it is placed on only one of the two current carrying paths and is calibrated to function when a current of between 8,000 and 12,000 amperes flows through the main circuit. The other device, magnet 500, attached to a longer main terminal 60, being subjected to the passage of all the current going through the breaker, is calibrated to act on currents in the order of 16,000 to 24,000 amperes and will be unaffected by the passage of smaller currents, thereby only functioning within its predetermined range.

In the foregoing I have described my invention solely in connection with specific illustrative embodiments thereof. Since many modifications and variations of my invention should now be obvious to those skilled in the art, I prefer to be bound not by the specific disclosures herein contained but only by the appended claims.

I claim:

1. In a circuit breaker having a pair of disengageable contacts, a spring normally urging said contacts into disengagement, a roller latch having a first position in which it defeats the action of the spring and a second position in which it permits the spring to operate, means for maintaining said roller latch in said first position, said means comprising a magnet, a first armature engaged by said magnet and a connection between said first armature and said roller latch, said spring through said roller latch exerting a force on said first armature tending to separate it from said magnet, said magnet during normal opera tion of said circuit breaker exerting a holding force on said first armature greater than that exerted thereon by said spring through said roller latch, said magnet releasing said first armature when the holding force thereof drops below the force exerted on said first armature by said spring through said roller latch, said magnet having a second armature on the opposite side of said magnet from said first armature, means for biasing said armature away from said magnet, said second armature being arranged to move toward said magnet against the action of said biasing means when the force exerted by the magnet rises above a predetermined value, means operable by said second armature on such movement thereof aiding the action of said spring thereby releasing said roller latch.

2. In a circuit breaker having a pair of cooperable contacts, a first member for controlling the engagement of said contacts, a spring biasing said member in one direction, said member having a notch in one surface thereof, a pivoted member having a notch; said member being positioned so that its notch is opposite the notch of said spring biased member and forms a seating therewith; a roller in the seat formed by the two opposed notches, the roller having a line of tangential contact with the notch in said pivoted member along a line in said notch displaced from the central axis of said roller and furthest from its pivot, said spring biasing said member in a direction to bring the roller in a line of tangential contact with the notch in said spring biased member along a line in said notch furthest from said spring so that said spring through said roller produces a rotative force on said pivoted member and an electromagnet having an armature exerting a force on said pivoted member at right angles to said spring on said first member to prevent said pivoted member from being rotated by said spring; said electromagnet when de-energized releasing said second pivoted member which therefore is rotated about its pivot by the action of said spring through said roller, means responsive to short circuit conditions for releasing said force on said pivoted member, means operative under reverse current conditions for releasing said force on said pivoted member, and means operative under overload conditions for de-energizing said electromagnet.

3. In a circuit breaker having a movable contact; a second contact in engagement with said movable contact; a connecting arm notched at one end and movable with said movable contact; a roller seated in said notch; a spring applying a force to said movable contact tending to efiect disengagement of said contacts; said spring acting on said arm to bring it into line contact with said roller and exerting a portion of the spring force to produce a rotative force on said roller tending to roll it out of said notch; said roller in the notch acting as a stop for preventing disengagement of said contacts by said spring; a pivoted arm having a notch, said roller also being seated in the notch of said pivoted arm; a holding magnet having an armature secured to said pivoted arm for producing a force on said pivoted arm sufiioient to overcome the rotative force of said spring on said roller to prevent said roller from rolling out of the notch of said connecting arm, said armature on being released by said magnet permitting said pivoted arm to move under the action of the rotation of said roller until said roller has moved out of said notches, said spring thereupon operating said contacts to disengaged position, a second armature biased away from said magnet, said second armature under short circuit conditions being attracted to said magnet, a plunger connected to said second armature for prying said first armature from said magnet upon actuation of said second armature, means biasing said first armature to said magnet, a second means for opposing the action of said first means upon reverse current conditions, a manually operable link for prying said first armature from said magnet and means for releasing said first armature from said magnet under overload current conditions.

4. In a circuit breaker for direct current circuits, having a pair of cooperable contacts having an engaged and a disengaged position, means biasing said contacts to the disengaged position; a latch for defeating the action of said biasing means; a second means for locking said latch to defeat the action of said first means; electromagnetic means including a first armature responsive to a reverse flow of current in said circuit for controlling said second means, and thereby, when de-energized, controlling the disengagement of said contacts, means including a second armature and a bias for normally biasing said armature away from said electromagnetic means and responsive to predetermined overload currents of a relatively low rate of rise in said electromagnetic means for pulling said second armature to said electromagnet for controlling said second means, and thereby the disengagement of said contacts and a second electromagnetic means responsive to short circuit current value and having an armature operated by said second electromagnetic means when energized for controlling said second means and thereby the disengagement of said contacts.

DONALD I. BOHN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 779,003 Scott Jan. 3, .1905 1,030,811 Henry June 25, 1912 1,122,430 Scott Dec. 29, 1914 1,123,288 Hellmund Jan. 5, 1915 1,248,084 Curtis Nov, 27, 1917 1,408,243 Austin Feb. 28, 1922 1,425,700 Scott Aug. 15, 1922 1,703,353 Natalis Feb. 26, 1929 1,926,989 Gernert Sept. 12, 1933 2,043,879 Bentley M June 9, 1936 2,150,566 Scott, Jr Mar. 14, 1939 2,340,973 May et al. Feb. 8, 1944 2,412,247 Bohn Dec. 10, 1946 2,419,892 Graves, Jr Apr. 29, 1947 FOREIGN PATENTS Number Country Date 445,215 Germany June 2, 1927 

